کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
1447799 988656 2010 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Effects of surface roughness and training on the twinning stress of Ni–Mn–Ga single crystals
موضوعات مرتبط
مهندسی و علوم پایه مهندسی مواد سرامیک و کامپوزیت
پیش نمایش صفحه اول مقاله
Effects of surface roughness and training on the twinning stress of Ni–Mn–Ga single crystals
چکیده انگلیسی

Spark eroding, which is commonly employed to cut samples out of magnetic shape-memory alloy single crystals, produces a rough surface layer. Directly after cutting, the single crystals exhibit a high twinning stress. After removal of a surface layer by electropolishing, the twinning stress reduces significantly and stress–strain curves become serrated. The reduction of twinning stress has previously been attributed to the removal of the defective surface layer. In this work, it is shown that different surface treatments in combination with repeated mechanical deformation experiments significantly reduce the twinning stress, regardless of whether or not electropolishing is used. The reduction of the twinning stress is due to softening that takes place as a mechanical training effect, which occurs with mechanical testing. In addition, the stress–strain curves of samples subjected to different surface treatments differed in so far as the curves of electropolished samples showed serrated flow, while the curves of unpolished samples and those of mechanically polished samples were smooth. Furthermore, the unpolished samples displayed significant hardening at higher strain. Following subsequent mechanical polishing, this hardening reduced to nearly zero, and the average twinning stress decreased another 30–50% to 1.6 MPa and below. For these samples, the twinning stress stayed at a very low level until twinning was complete.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Acta Materialia - Volume 58, Issue 11, June 2010, Pages 3952–3962
نویسندگان
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